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Date:   Tue, 3 Oct 2017 13:43:30 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Christophe LEROY <christophe.leroy@c-s.fr>
Cc:     Christoph Hellwig <hch@lst.de>, iommu@lists.linux-foundation.org,
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Subject: Re: [PATCH 07/11] powerpc: make dma_cache_sync a no-op
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On Tue, Oct 03, 2017 at 01:24:57PM +0200, Christophe LEROY wrote:
>> powerpc does not implement DMA_ATTR_NON_CONSISTENT allocations, so it
>> doesn't make any sense to do any work in dma_cache_sync given that it
>> must be a no-op when dma_alloc_attrs returns coherent memory.
> What about arch/powerpc/mm/dma-noncoherent.c ?
>
> Powerpc 8xx doesn't have coherent memory.

It doesn't implement the DMA_ATTR_NON_CONSISTENT interface either,
so if it really doesn't have a way to provide dma coherent allocation
(although the code in __dma_alloc_coherent suggests it does provide
dma coherent allocations) I have no idea how it could ever have
worked.